Cooling

Cooling requirements become more stringent as the alloyage level increases.

The most commonly used alloys, EN AW-6060 and EN AW-6063, can usually be air-cooled. Harder alloys need to be cooled with water mist, and alloy EN AW-6082 requires fast and powerful water cooling.

The requirements demand that materials are cooled from the runout temperature to below 200ºC within the times specified in the table below:

fig1_eng

Generally, the more forced cooling is used, the greater the effect on the dimensional outcome of the extruded profile.

Uneven material thicknesses, asymmetrical profiles and excessive cooling are always problems. Uneven cooling of the cross-section results in spurious thermal stresses that may create problems during subsequent handling and processing of the profile